The application of a carbon nanotube (CNT) to a via material of LSI wiring has been vigorously developed worldwide. In the via formation by the carbon nanotube, a catalyst underlayer is formed on a side surface and a bottom surface of a via hole, and a catalyst layer is formed on the catalyst underlayer. A carbon nanotube is grown from the catalyst layer and is buried in the via hole.
In this case, since the catalyst layer and catalyst underlayer are formed on the side surface of the via hole, carbon nanotubes, which do not contribute to electrical conduction, also grow from the side surface of the via hole. Since electrical conduction by the carbon nanotubes which have grown from the side surface of the via hole, is electrical conduction via a barrier metal on the side surface of the via hole, the via resistance is greatly increased. In addition, there is concern that the upper part of the via hole is filled with the carbon nanotubes which are grown from the side surface of the via hole, and the circuit is, in fact, broken.
In order to suppress growth of carbon nanotubes from the side surface of the via hole, there is known a method of forming a catalyst deactivation layer between the catalyst layer and catalyst underlayer at the side surface of the via hole. In this method, in order to grow the carbon nanotubes from the bottom surface of the via hole, it is necessary to remove, by etch-back, the catalyst deactivation layer which is formed on the bottom surface of the via hole.
However, in the via hole with a high aspect ratio, it is very difficult to surely remove the catalyst deactivation layer on the bottom surface of the via hole. In addition, when the catalyst deactivation layer is etched back, it is possible that the catalyst underlayer is damaged and the growth of the carbon nanotubes is hindered.